The invention concerns a differential pressure transducer wherein a change in pressure produces a bending of an internal part. The amount of bending is measured to provide an indication of the amount of the pressure change.
It is conventional for such a differential pressure transducer to include a closed measuring chamber formed by at least two measuring membranes which are interconnected by means of a coupling part. The coupling part is connected to a bending bar to bend the latter so that the extent of such bending can be measured to provide an indication of the amount of the pressure change.
Known difference pressure transducers of this type operate on the so-called single chamber principle in which the bending bar is located within the measuring chamber formed by the two measuring membranes and is indirectly connected to both membranes by the coupling part. The measuring chamber is filled with a liquid and since it contains the bending bar, it has a relatively large volume. This volume varies with temperature so that the measured values of the known differential pressure transducer are strongly temperature dependent. Furthermore, during such volume changes and in case of an overload, the measuring membranes are severely stressed. In addition, careful attention must be given in the selection of materials for the known transducer if the pressure media to which the measuring membranes are exposed comprise an aggressive liquid or the like. In such a case, the types of material (and thus the properties of the membranes) which can be chosen are limited.
Differential pressure transducers operating under the so-called two-chamber principle, are also known (see German Pat. No. 33 41 987). In such differential pressure transducers, the movement of the measuring membranes separating the two measuring chambers are measured, for example, by means of a path measuring system or a force measuring system. A particular problem regarding the two-chamber difference pressure transducers involves the fact that the measuring membranes must be protected against excessive stretching in both directions.
It is an object of the invention to provide a differential pressure transducer that is largely independent of temperature and which contains a measuring membrane protected against overloads in a simple manner.